High-temperature heatings made from graphite materials must be operated in a gasproof, air-free heating zone. The electrical supplies must be conducted through the wall of a dense and comparatively cold case.
Two-zone graphite heatings that are arranged one above each other, for vertically erect (reaction) chambers, can be arranged directly on top of each other separated from each other by insulating components. The electrical supplies of a heating zone, however, must be able to balance out the difference in length of the heater compared to the case caused by different thermal expansibility.
From the third heating zone on, however, the electrical supplies of the central heating zones must be conducted radially out of the heating zone. These can now be conducted radially and flexibly (by means of cooled metallic materials) through the side wall of the case or with large-design graphite electrical supplies outside the heating vertically upward or downward which, however, requires flexible, metallic connections. Particularly in the case of very big heaters (e.g. up to 10 m height) lateral connection causes great problems during assembly.
In the case of large-design high-power heaters which are often operated at low voltage (with the consequence of even bigger-and heavier-dimensioned parts) the electrical supplies of the heating zones that are arranged one above the other are very heavy and the whole construction becomes mechanically more and more unstable the higher the construction is and high Carbon Fiber Composite (CFC) heating elements can no longer carry the weight of the above heating zones with their electrical supplies. Therefore subframes become necessary for the individual heating zones comprising separate supports resting outside the heating.